1. Field of the Invention
The invention relates to an image forming unit and an image forming apparatus.
2. Description of Related Art
An image forming apparatus such as a printer, a copier, a facsimile apparatus or a multifunction machine includes an image forming unit. Specifically, in the printer, for example, an image forming unit for forming a toner image on a surface of a photosensitive drum is disposed to be freely attached to and detachable from a printer main body, that is, an apparatus main body. Moreover, the image forming unit includes: a main body of the image forming unit, that is, an image forming unit main body; and a toner cartridge for containing a toner as a developer, the toner cartridge being disposed to be freely attached to and detachable from the image forming unit main body.
A housing of the image forming unit main body includes: a toner supply port formed to face the toner cartridge and configured to supply the toner into the image forming unit main body from the toner cartridge; a light receiving port formed to face an LED head and configured to expose the photosensitive drum with light generated by the LED head; and a transfer port formed to face a transfer roller and configured to transfer the toner image onto paper as a medium.
Among these ports, the light receiving port and the transfer port are required to have an opening width equal to or larger than a width of a printing area in order to access the printing area on the paper. Here, the toner supply port preferably has sufficient opening width as to allow the toner supplied into the image forming unit main body to easily spread all over the area in a rotation axis direction of the photosensitive drum in the image forming unit main body.
In the image forming unit, the toner supply port, the light receiving port and the transfer port are simultaneously formed during formation of the housing of the image forming unit main body with synthetic resin. However, during a cooling step in the formation process, deformation, warpage and the like are likely to occur in the housing.